A UNIX system can have hundreds or thousands of directories - and a lot
more files.
Even if you remember all the pathnames, typing them over and over can be a pain.

Your account probably already has some helpful
shell and environment variables (
6.8
,
6.1
)
set up.
You can add more from the command line or from your
shell setup files (
2.2
)
(like
.cshrc
or
.profile
).
To see what environment variables are set, use the
env
(System V) or
printenv
(Berkeley) command.
The command
set
should show shell variables (some of these might
be repeated in the environment).
Here's part of what happens on my account:

UNIX programs use a lot of those environment variables.
For instance, my email system finds its setup file from
MH
.
But I can use environment variables for other things, too.
For instance, when I want to edit my email setup file, I can type
vi $MH
from any directory.
The shell expands
$MH
to
/work/jpeek_mail/.mh_profile
and starts
the editor.
Check your environment and see what you've got; the names usually
explain the variables pretty well.

The shell uses shell variables like
$mail
.
I can check incoming messages with the command
tail $mail[2]
(
25.14
,
47.5
)
(the
[2]
tells the C shell to pick the second word from the list in
$mail
).

I've set other shell variables for myself.
When I send some mail messages, I want to watch the system mail log to
see the message being delivered.
I just type:

Are there files or directories that you refer to a lot - ones that aren't
right for the
cdpath
(
14.5
)
or a shell alias?
Pick a likely shell variable name and add the variable to your
.cshrc
or
.profile
.
You can store more than one pathname in the same variable - either by
separating them with spaces or by using wildcards:

# C shell variables:
set worklog=~/todays_worklog
Single file, defined when set
set projfiles=(/work/beta/data_3.9*)
Many files, defined when set
set currdata='/work/beta/data_5*'
Many files, defined when used
# Bourne shell variables:
worklog=$HOME/todays_worklog
Single file, defined when set
projfiles="`echo /work/beta/data_3.9_*`"
Many files, defined when set
currdata='/work/beta/data_5*'
Many files, defined when used

Then:

You could type
vi + $worklog
any time you want to add a note to the end
of the file
todays_worklog
in your home directory.
(The
+
tells
vi
to start at the end of the file.)

The shell expands the asterisk (
*
) when it sets the
projfiles
variable and stores a list of the files
as they were when the
variable was set
.
(If the list of files changes, it'll be reset when you start your next shell.)
You could print all those files any time you wanted to by typing a
command like
lpr $projfiles
.
The C shell also lets you
pick individual files (
47.5
)
from the list - for
instance,
lpr $projfiles[9]
would print the ninth file from the list.

When the
currdata
variable is set, the single quotes (
"
)
around it
prevent expansion (
8.14
)
of the wildcard (
*
).
Instead, the pathname
/work/beta/data_5*
is expanded when you use
the variable - like
pg $currdata
- to show
you the files as they
are at the time you use the variable.

You can also use variables to store the paths to directories.
Use
cd
,
ls
, or any other command with the variables.